In the oil and gas industry, various sensor systems or packages have been developed for placement on or near the drill bit. Such sensors permit characterization of subsurface formations as the bit approaches or enters the formation, minimizing unnecessary drilling. Also, the trajectory of the drill bit may be adjusted in response to the characterization. However, to effectively use such sensors and perform such adjustments, the sensed data must be communicated to the surface.
It is common to have a telemetry sub in the bottomhole assembly that can communicate with the surface via an internal tool bus among other tools in the bottomhole assembly. Yet that telemetry sub is separated from the bit by a mud motor and/or steering assembly which, due to the high torques, high stresses, and high relative rotation rates created within these units, have not permitted the installation of tool bus wires in the standard fashion.
This situation creates a need for a “short-hop” telemetry system to bridge the communications gap between the at-bit sensors and the wired tool bus of the bottomhole assembly. Various systems have been proposed for such short-hop communications, including the use of electromagnetic fields and currents in the bottomhole assembly. These systems may be inordinately complex and expensive.
It should be understood, however, that the specific embodiments given in the drawings and detailed description thereto do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.